package train48days;
import java.util.*;

/**
 * 找规律
 */
public class 杨辉三角的变形 {
        public static void main(String[] args){
            Scanner in = new Scanner(System.in);
            while(in.hasNext()){
                int n = in.nextInt();
                if(n<=2)
                    System.out.println(-1);
                else if(n%2==1){
                    System.out.println(2);
                }else{
                    if(n%4==0)
                        System.out.println(3);
                    else
                        System.out.println(4);
                }
            }
            in.close();
        }
    }